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Lower Blood Pressures and Mortality in Very Old Persons

Am Fam Physician. 2008 Jan 1;77(1):94.

Background: Despite an aging population, there are few data on target blood pressure in very old persons (at least 80 years of age), an age group that has been under-represented in clinical trials. Excessively lowering blood pressure in this population could result in complications such as falls, strokes, mental confusion, or depression. Population-based studies have suggested that higher blood pressure is associated with improved survival rates. Conflicting studies have shown decreased cardiovascular events in patients with lower blood pressure, but no benefit in relation to all-cause mortality. Oates and colleagues sought to identify a relationship between baseline blood pressure and five-year survival rates in patients 80 years or older with hypertension.

The Study: A subsample of 4,071 patients at least 80 years of age with hypertension were studied retrospectively using clinic data from a larger study of veterans. For 1,289 of these patients, data were extracted from a health-related quality of life survey and inpatient vital statistics, as well as death information from various sources. The study spanned 18 months.

Results: Participants averaged 82.6 years of age and had a mean systolic blood pressure of 148 mm Hg and a mean diastolic blood pressure of 72 mm Hg. Patients with comorbidities, such as diabetes mellitus and cardiovascular disease, were well represented in the study. Almost one half of the participants (1,913 persons) died during the study.

Patients with blood pressure below the recommended level (systolic blood pressure lower than 140 mm Hg) had a higher mortality rate than patients with a 10-point increase in systolic blood pressure over the target range. The unadjusted hazard ratio (HR) was 0.79 (95% confidence interval [CI], 0.75 to 0.84), and the adjusted HR was 0.84 (95% CI, 0.78 to 0.89). Similarly, for a 10-point increase in diastolic blood pressure over the target range of less than 90 mm Hg, the unadjusted HR was 0.86 (95% CI, 0.82 to 0.91) and the adjusted HR was 0.91 (95% CI, 0.87 to 0.96). The results for the health-related quality of life survey subgroup were similar, but did not reach statistical significance.

Conclusion: In this study, very old patients with hypertension who had their blood pressure lowered to the conventional target range had lower survival rates than those with blood pressure conventionally considered uncontrolled. The reason why patients in this age group who had controlled blood pressure had worse survival rates may be related to falls, orthostasis, or other adverse effects of medication. Conversely, the benefit of higher blood pressure may be related to better organ perfusion. Some limits of the study were that it was retrospective, predominantly limited to men, and did not evaluate the cause of death. The authors conclude that lowering blood pressure below 140/90 mm Hg in a very old population may put patients in this age group at higher risk of mortality.